It has long been recognized that rabbit antibodies have favorable properties compared to mouse antibodies. First, rabbits are known to produce antibodies to many antigens that are poorly immunogenic in mice (e.g., Norrby et al., Proc. Natl. Acad. Sci. 1987 84:6572-6; Raybould & Takahashi, Science 1988 240:1788-90 and Weller et al., Development 1987; 100:351-63). For example, Bystryn et al (Hybridoma 1982 1:465-72) directly compared rabbit and mouse antibodies directed against human melanoma cells and showed that they recognize different epitopes. Second, rabbit antibodies are generally of high affinity. Third, because most monoclonal antibodies are generated in mice and rats, relatively few monoclonal antibodies are available that react with mouse or rat immunogens. In spite of these advantages, until recently it has been impossible to raise monoclonal antibodies in the rabbit. Monoclonal antibodies are predominantly produced by using the hybridoma technology originally developed by Koehler and Milstein (Nature 1975 256:495-7). This method involves immortalization of antibody-producing lymphocytes by fusion with myeloma cells. Since myeloma-like tumors are unknown in the rabbit, it has been impossible to use this approach for producing rabbit monoclonal antibodies. Attempts have been made to use mouse myeloma cell lines as fusion partners (e.g., Raybould & Takahashi, 1988, supra), or to use in vitro-transformed lymphoid cell lines from rabbits, but in all cases these approaches were hampered by the instability of the resulting hybridomas.
A novel approach was taken by K. Knight and colleagues (Spieker-Polet et al., Proc. Natl. Acad. Sci. 1995 92:9348-52), who succeeded in producing a myeloma-like tumor in transgenic rabbits expressing oncogenes under the control of the immunoglobulin heavy and light chain enhancers. They isolated a plasmacytoma cell line, termed 240E-1, from these tumors, and showed that fusions of 240E-1 cells with rabbit lymphocytes produced hybridomas. Hybridomas were produced from lymphocytes of rabbits immunized using plasma proteins or whole cells, and were shown to secrete IgG antibodies.
An improved fusion partner cell line for the production of monoclonal antibodies from rabbits is provided.